The astronauts aboard the linked shuttle and space station geared up to inspect a damaged thermal blanket on Atlantis on Sunday after their main job - installing the Columbus lab - was delayed a day because of a crew medical problem.

German astronaut Hans Schlegel was pulled off the first spacewalk of the mission shortly after he arrived at the international space station Saturday aboard Atlantis. Managers bumped the spacewalk and Columbus' hookup to the space station to Monday.

NASA declined to discuss the medical problem beyond saying it was not life-threatening, but a European flight controller confirmed Sunday that Schlegel was ill.

"We're all keeping our fingers crossed for him to get better soon," he said.

Schlegel, 56, a two-time space flier, sounded OK on Sunday morning when he spoke to Mission Control after waking up to music from fellow German Herbert Gronemeyer.

"Greetings to everybody in America, in Europe and in Germany, and especially of course to my close family and my lovely wife, Heike," he said.

Schlegel was supposed to venture outside with American Rex Walheim on the first two of three planned spacewalks. His status on the second spacewalk, on Wednesday, was still uncertain.

The Columbus lab should have been unloaded from Atlantis and attached to the space station on Sunday, with two spacewalkers outside to help. Mission Control informed the astronauts that the installation would not take place until Monday just a few hours after the shuttle and the station joined up.

NASA said Schlegel's shuttle crewmate, American Stanley Love, would take his place. Love trained for the work as a backup, just in case, and already was assigned to the mission's third spacewalk, along with Walheim.

Shuttle commander Stephen Frick asked Mission Control on Sunday to clear Schlegel's schedule the following day so he could help guide Love from inside the station.

After spending much of the morning preparing for Monday's spacewalk, the crew will use cameras and a robotic arm to gather more images of a 1½-inch by 1½-in protrusion on one of the many blankets covering Atlantis' right orbital maneuvering system pod, back near the tail.

Space station flight director Ron Spencer said early Sunday that NASA did not know if the blanket was torn or if it was just sticking up a bit.

Engineers were trying to determine whether the damage posed a hazard for re-entry at flight's end. The peeled-up section is smaller than one that required spacewalking repairs to Atlantis in June.

NASA is particularly attentive to the shuttle's thermal shielding, ever since Columbia was destroyed during re-entry in 2003.

The delay in installing Columbus and carrying out the first spacewalk caused NASA to add a 12th day to the mission. Yet another day could be added; NASA had hoped to spend an extra day at the space station to help set up Columbus. Atlantis will remain at the orbiting complex until at least next weekend.